Heat exchange apparatus



' P 1951 E. a. LOPKER 2,566,929

l-lEAT EXCHANGE APPARATUS Filed Dec. 10, 1947 4 Sheets-Sheet 1 INVENTOR.

EDWIN B. LOPKER Sept. 4, 1951 V E. B. LOPKER HEAT EXCHANGE APPARATUS 4Sheets-Sheet 2 Filed Dec. 10, 1947 INYENTOR.

ATTORNEY.

I I /I P 1951 E. B. LOPKER 2,566,929

HEAT EXCHANGE APPARATUS Filed Dec. 10, 1947 4 Sheets-Sheet a 1.1- T5 5FIGS. g

r8- INVENTOR.

EDWIN a LOPKER gead/zz g AT TORNEY.

Sept. 4, 1951 Filed Dec. 10, 1947 HEAT EXCHANGE APPARATUS 4 Sheets-Sheet4 FIG.| I. 54 FIG.9. 5 FIG.|2.

4/ 57- '58 (I, 2 6/ 3O 42 ,1" I 5/ 5 52 v V /64- --57 FIG. IO. v 45 FIG.I5. F FIG.I3. FIG. I6.

7 --a/ 78 1 7% 84- (f I 7 0 7 0 7/ '84 FIG. l4.

' INVENTOR. I EDWIN B.LOPKER ATTORNEY Patented Sept. 4, 1951 HEATEXCHANGE APPARATUS Edwin B. Lopker, East Orange, N. J., assignor toAllied Chemical & Dye Corporation, New York, N. Y., a'corporation of NewYork Application December 10, 1947, Serial No. 790,848

This invention relates to heat exchangers, and

Claims. (01.257-256) particularly to cooling apparatus, adapted for usein the manufacture of e. g. sulfuric acid, of the type in which the acidor other fluid to be cooled is flowed in the form of a ribbon or thicksheet between relatively closely arranged metallic heat transfer wallswhich are externally cooled by a cooling medium such as water.

In acid cooling apparatus of the kind to which this invention relates,it is important to maintain turbulence and to effect a complete breakingup or thorough mixture of all portions of the acid layer or ribbon beingcooled in order to prevent the formation of a central core of relativelyuncooled acid interiorly of the acid ribbon as the latter flows betweenthe externally watercooled side walls of the cooler. In order to providefor the foregoing, in prior apparatus, design has been such as to spacethe acid passage side walls rather close together, thus restricting thethickness of the acid layer or ribbon. Further, the area of heattransfer metal in contact with the acid is relatively fixed. Thesefactors limit the capacity of a unit of given rectilinear dimensions.

The principal object of my invention is to increase the capacity ofcoolers of the type indicated and thereby decrease the number of unitsrequired for a given installation.

In accordance with this invention, I find that it is possible, incoolers of the kind mentioned,

, to substantially increase the area of heat transfer metal in contactwith acid to be cooled and still maintain structural aspects which areneeded to prevent core formation. By so doing, I am enabled tosubstantially increase the thickness of the acid layer andcorrespondingly increase the capacity of a cooler unit of givenrectilinear dimensions.

The invention, its objects and advantages may be understood from thefollowing description taken in connection with the accompanyingdrawings, in which Fig. l is a partial front elevation, of the coolerunit of Figs. 1-4, taken on line l-l of Fig. 3;

Fig. 2, looking in the direction of the arrows of lines 22 of Figs. 3and4, is an elevation of a portion of the inside face of the rear sideplate or casting of such cooler unit;

Fig. 3 is a horizontal section taken on lines 3-4 of Figs. 1, 2 and 4;

Fig. 4 is a vertical section taken on line 4-! of Fig. 1;

Fig. 5 is a partial front elevation, of a modifled cooler unit of Figs.5-8, taken on line 55 of Fi 7;

Fig. 6, looking in the direction of the arrows of lines 66 of Figs 'land 8, is an elevation of a portion of the inside face of the rear sideplate or casting of such modified cooler unit;

Fig. '7 is a horizontal section taken on lines 1--| of Figs. 5, 6 and 8;

Fi 8 is a vertical section taken on line 8-8 of Fig. 5;

Figs. 9-16 inclusive are diagrammatic sketches hereafter discussed; and

Fig. 17 is an enlarged detail.

Referring to Figs. 1-4 of the drawing, representing a preferredembodiment of the in.vention, the imporved cooler comprises verticallydisposed front and rear side plates I0 and II preferably constructed ofcast iron. Rear plate or casting II, the inner or acid side of which isshown fragmentally in elevation in Fig. 2, comprises a side wall sectionI! bounded on either vertical side edge by coplanar flanges I4 and Hi.The upper horizontal edge of wall section I! terminates in an upperhalf-header portion l6, and the lower horizontal edge of section IImerges with lower half-header portion H. The upper and lower headerportions are each provided with vertical flanges 20 and 2| which arecoplanar with side flanges l4 and I5. On each end of each half-headersection is a semicircular flange 23. Flanges ll, I5, 20, and 2| aredrilled as at 25 to accommodate bolts by means of which front and rearplates l0 and II may be attached together to form a unitary structurewhich comprises spaced apart side wall sections, an upper horizontalheader for inflow of acid to be cooled, and a lower outlet header fordischarge of liquid from the unit. The flanges on the ends of thehalf-header inlet portions afford means for connecting the unit shown toother cooling units or to suitable acid inlet and outlet pipes.

In accordance with the invention, while side wall section I: may be ofany suitable form, preferably such section is made up of a series ofhorizontally disposed corrugations of relatively Z-shaped configuration,as shown on Fig. 4. A particular embodiment of the invention compriseswall section structure in which the terminal slopes of the wall section(as viewed in Fig. 4) adjacent opposite edges are substantiallyparallel. In the construction of a side wall. the angle A may be acuteor obtuse and of any suitable angular value, but ordinarily lies withinthe range of -105 degrees and is preferably about degrees. A corrugationleg length (distance B, Fig. '4) may vary substantially. However, in thepreferred embodiments of the invention, the particular values .for angleA and leg length 8 are so chosen and correlated that the apex, e. g. at21, of each convex surface of the inner side wall extends at least toand preferably thru a vertical a vertical plane passing thru the,longitudinal axes of the upper and lower headers. existence of astraight line downflow of an unbroken core of acid from the upper to thelower header.

A major feature of the invention which makes it possible to space theside ,wall secti'ons rela'- tively far apart, and therebylargely'increase the capacity of the unit of given rectangulardimensions, and at the same time maintain the turbuplane which isdisposed at a right angle to the This construction prevents the lenceand effect complete breaking up and thorough mixture of all portions ofthe acid ribbon being cooled in order to prevent the formation of acentral quiescent core of relatively uncooled acid, is the provision ofinwardly projecting ribs on the inner face (the acid side) of wallsection l2. Such ribs, when viewed in elevation as in Fig. 2, may takevarious forms in accordance with different modifications of theinvention. Usually these ribs are cast integrally on the acid side ofthe wall section and the transverse surfaces thereof lie in planes whichare disposed preferably at a right angle to the general vertical planesof side wall section l2.

In a preferred embodiment of the invention, Figs. 1-4, the ribsindicated generally by 30 appear in elevation (Fig. 2) as a series ofcorrugations of configuration broadly similar to that of the corrugatedside wall portion (2 itself as .shown in vertical section in Fig. 4.Each of ribs 30 is cast onthe inner face (acid side) of wall section l2so that the entire rib edge, remote from the inner face of wall sectioni2, lies in a vertical plane which passes thru the longitudinal axes ofthe upper and lower headers. This u construction may be observed fromFig. 4 which shows that the innermost edges of all of ribs 30 and theinner faces of top and bottom flanges and 2| and of side flanges l4 andI5 all lie in a common plane which includes the longitudinal axes oftheupper and lower headers when the unit is assembled. Such arrangement andmode of casting of the ribs on the inner face of a side I obtuse, but inorder to obtain good commercial results, angle C ordinarily lies withinthe range of 75-105 degrees. Preferably, angle C is approximately thesame value as angle A of Fig. 4, and notably good acid turbulence ismaintained when angles C and A are both approximately 90 degrees. Leglength, distance D Fig. 1'7, of a sin le wave or corrugation of a ribmay likewise vary to a considerable extent. The spacing apart of theribs, distance E, is subject-to substantial variation. Preferablydistance E is less than leg length D, and spacing apart of the ribsshould be such as to provide a relatively narrow channel between twoadjacent ribs. Further, if desired, in the more desirable forms of thinvention when angle C-is about 90, spacing-apart distance E and leglength D may be so chosen and correlated that (1) straight line (linearvtravel of an acid particle thru a channel is not substantially more thanspacing apart distance E, and (2) the apex, e. g. 36 of rib 34,

related to the foregoing feature.

vertical plane of wall section I! and which passes thru the apices 38and 39 of the adjacent convex surfaces of the adjacent rib 33, thevertical trace of such a plane being represented by theline F-F of Fig.17. This arrangement prevents uninterrupted straight-line downflow ofacid between two adjacent ribs, e. g. 33 and 34.

An important feature of all forms of the invention in which ribs 30 arewave-like or corrugated (when viewed in elevation as in Fig. 2), i. e.when the projection of the length of the rib on a plane parallel to thegeneral planes of the wall sections is wave-like, corrugated orZ-shaped, and in which the side wall sectionsof the cooler are alsowave-like or corrugated (as shown in the section of Fig. 4), is that thedesign of each rib 30 is such that the terminal slopes 4| and 42 ;(Fig.2) of a given rib are relatively parallel. 'I'hus, ribs 30 are formed sothat an individual rib 30 is not made up of a plurality of complete wavelengths but comprises a plurality of, complete wave lengths plus a halfwave length}, and because of this arrangement the courses of theterminal slopes of such rib are parallel rather than at right angles.The reason for this construction hereinafter appears.

Two major modifications of the embodiment of the invention illustratedin'Figs. 1-4 are closely In the first modification, e. g. the frontplate It is cast in a mold which is the same as the mold used forcasting the rear plate ll except that the mold employed for casting thefront plate It is made so that the elevational configuration of the ribs45 (Fig. 1) as cast on the inner side (acid side) of the front side wallsection l3 are mirror patterns of the ribs on the inner side of the rearwall section l2, i. e. the projections of the ribs of one section on aplane parallel to the general planes of the wall sections are mirrorpatterns of similar projections of the ribs of the other sec-. tion. Inthe second modification, both the front and rear plates Ill and I I arecast in molds which are identical throughout. For convenience ofdiscussion, these two modifications may be hereinafter referred to asmirror patterns and "identical patterns.

The selection of mirror or identical rib patterns is of importance indetermining the structure of.

the cooler desired. As previously observed, the cooler unit is assembledby bolting a front and rear plate together at vertical edge flanges l4and I5 and at horizontal upper and lower header flanges 20 and 2!. Therelation between mirror and identical rib patterns and the differencesbeis the same in all other respects as the Fig. 9 casting except that inFig. 10 the ribs 45 are mirf ror patterns of the ribs 30 of Fig. 9. Itwill be seen that when the casting of Fig. 10 is turned up out of theplane of the paper and rotated about edge 5|, and the inside of the Fig.10 casting is placed in abutting relation with the inside of the castingof Fig. 9, and so that edge 5| of Fig. 10 coincides with edge 52 of Fig.9 and edge 54 of Fig. 10 coincides with edge 55 of Fig. 9, the resultingunit construction is such that corresponding ribs 30 and 45 abut (exceptfor the thickness of the gasket between the edge and top flanges) andare exactly coextensive. The unit appears in front elevation as shown inFig. 12 in which the dotted line indicates a Z-shaped partitionextending across the .interior of the cooler unit and made up by theabuttting and coextensive ribs 30 and 45. If the same casting of Fig.were turned end-for-end it would appear as in Fig. 11. Further, if theinside of the casting in the position of Fig. 11 is then turned over 180into abutting relation with the inside of the Fig. 9 casting, and sothat edge 58 of Fig. 11 coincides with edge 60 of Fig. 9 and edge 51 ofFig. 11 coincides with edge SI of Fig. 9, the resulting constructionwith respect torib arrangement will be the same as before, i. e. asshown in Fig. 12 in which corresponding ribs on the opposite sides ofthe unit abut and form coextensive partitions across the cooler unit.

As was noted above, terminal slopes II and 42 of a rib 30 of Fig. 2 areparallel. This same relation is shown in Fig. 9, and it will be seenthat although a rib 45 of Fig. 10 is a mirror pattern of a rib 30 ofFig. 9, the terminal slopes 64 and 65 of a Fig. 10 rib are alsoparallel. In accordance with the invention, it has been determined thatwhen the interior ribs are wave-like or corrugated and when the sidewall sections of the cooler are also wave-like or corrugated, theterminal portions of the ribs should be parallel so that when the frontand rear wall sections are bolted together to form a unitary cooler, thewaves or corrugations of the side wall sections mesh (as shown in Fig.4) and form outer walls which are parallel even though of wave-like orcorrugated formation. It will be appreciated that the foregoingdiscussion relative to Figs. 9-12is descriptive of the assembly of theFigs. 1-4 modification which is made up in mirror pattern ribs.

Figs. 13-16 diagrammatically illustrate assembly and final constructionof a unit made from two castings having identical rib patterns. Fig. 13indicates in elevation the ribbed inside of a wall section the same asshown in Fig. 2. Fig. 14 represents in elevation the ribbed inside of awall section which in all respects is identical with the wall section ofFig. 13. If the wall section of Fig. 14 is turned up out of the plane ofthe paper and rotated 180 so that the inner faces of both sections abutand so that edge 10 of Fig. 14 coincides with edge H of Fig. 13 and edge13 of Fig. 14 coincides with edge 14 of Fig. 13 the resulting unit whenviewed in front elevation will appear as in Fig. 16. From the latter, itwill be noted that a rib 11 of Fig. 14 abuts a rib 18 of Fig. 13 atspaced intervals but that such abutment of corresponding ribs is incriss-cross preferably right-angled relation. If the wall section ofvFig. 14 is turned end-for-end as shown in Fig. 15, and turned over 180so that the inside of the wall section of Fig. 15 contacts the inside ofthe wall section of Fig. 13 and so that edge 80 of Fig. 15 coincideswith edge 8| of Fig.

13 and edge 84 of Fig. 15 coincides with edge 85 of Fig. 13, theresulting cooler unit is the same as shown in Fig. 16. It is noted thatthe terminal portions of the rib 18 of Fig. 13 are parallel, and thatthe same is true with respect to the rib ll of Fig. 14. This parallelismof rib terminal portions provides a construction, in the case ofidentical patterns as well as in the case of mirror patterns, by whichit is possible to insure the meshing relation of the corrugations of theoutside wall sections.

Referring again to Figs. 1-4, it will be noted that the upper end ofeach channel between two adjacent ribs 30 opens into the upper header,and the lower end of such channel discharges into the lower header. Inthis embodiment of the in vention, the coextensive relationship ofcorresponding ribs on the rear and front wall sections l3 and I2 isillustrated particularly in the section of -Fig. 3 which shows thatcorresponding rear and front ribs form unbroken partitions extendingtransversely of the cooler unit, and that any two adjacent partitionsform a channel which in horizontal section is elongated transversely ofthe cooler unit. Such channel provides for a ribbon or stream of acid tobe cooled having a horizontal crms-sectional area corresponding with thehorizontal cross-sectional area of the channel.

As more clearly shown in the enlarged detail of Fig. 17, the ribs areconstructed preferably to provide a plurality of sharply inclinedreversely extending surfaces against which the acid in the channel 90impinges. After the acid flows downwardly in one portion 92 of a channel90, an abrupt change in the direction of flow produced by the sharpconcave turn of the rib 33 causes the relatively sluggish skins of acidparticles, formerly in contact with opposing faces of the ribs, and thefaster moving central core of acid, which was not in direct contact withthe surface of either rib, to be vigorously churned up and thoroughlymixed. As the acid flows to the end of the next lower and oppositelyinclined portion 91 of channel 9!), a similar though oppositely disposedturbulence and mixing of the acid is effected. It will be observed thatthe ribs are provided with a plurality of convex surfaces e. g. 36 (Fig.17) and a plurality of concave surfaces lllll connected by inclinedsurfaces e. g. Illl. Thus, the acid between two adjacent ribs isprojected successively across each passage 90 from one rib to theadjacent rib. It will be understood that the shorter the lineal lengthof the inclined surfaces, the greater will be the turbulence of the acidflowing between two adjacent ribs, the maximum effect being obtainedwhen the linear straight line travel lengths of inclined portions 92 and91 are not substantially longer than the width of each channel 90.However, as will hereafter more fully appear, the invention is such asto greatly increase the metal heat transfer surface in contact withacid, and ac cordingly permits not only a substantial increase of thedistance between side walls l2 and I; (Fig. 4) but also a reduction inthe total number of corrugations in a side wall section If. Suchreduction entails a lengthening of a leg length B (Fig. 4), but doesaflord substantial manufacturing conveniences. l-Lecaus of the multipleturbulences effected by the combined action of ribs 30 and corrugatedside walls l2 and [3, according to this invention, short leg lengths, e.g. distances B and D of Figs. 4 and 17. are not required. I

The ribs 30 are formed and spaced so that the apex of an inner convexsurface 36 of one rib projects at least to and preferably thru avertical plane F as mentioned in connection with Fig. 17. Thisconstruction prevents an uninterrupted vertical descent of any liquiddirectly from the upper header to the lower header, and also preventsthe passage of liquid particles between adjacent ribs without causingsuch particles to be repeatedly projected from contact with one rib tocontact with another;

Referring to Fig. 2, it will be observed that the wave-like course orundulation of a ribbon of acid flowing downwardly between two adjacentribs 30 lies in a general plane disclosed at right angles to'the rearand front side wall sections 12 and II of the cooler unit. It will benoted also that, in the particular embodiments of Figs. 1-4, withrespect to leg lengths and angularities, the wavelike configuration ofthe rear and front walls l2 and 13 (Fig. 4) is similar to orapproximately the same as the configuration of a rib 30 (Fig. 2).Accordingly, it will be seen from a consideration of Fig. 4, thatcorrugated side walls I2 and i3 cause downfiowing acid to take the formof undulations similar to the undulations effected by ribs 30. However,since the general planes of side walls l2 and I3 are at right angles toribs 30, it will be understood that undulations effected by the sidewalls lie in a general plane parallel to the rear and front walls andare disposed at right angles to the undulations caused by ribs 30. Thatis, ribs 30 effect one set of downfiowing acid undulations while sidewalls I2 and i3 cause another set of undulations, the latter being atright angles to the former. Accordingly, it will be appreciated that thepreferred construction of the invention, comprising wave-like ribs andwavelike side wall sections, is such that the turbulence, core breaking,and acid mixing described above specifically in connection with theundulations formed by the configuration and spacing of ribs 30 aresubstantially duplicated by the configuration and spacing of side wallsl2 and I3. Further, since the two sets of wave-like courses orundulations are disposed at an angular relation to each other, theparticles of downflowing acid are being continuously transferred fromone set of undulations to another, and the invention providesconstructions which multiply acid turbulence and mixing severalfold. Itwill be apparent; therefore, that the wave-like constructions of theribs 30 and of the side walls l2 and I3 together repeatedly causevigorous breaking up and reversal of all parts of the fluid stream beingcooled and effect thorough admixture of all increments of acid. Sincedirection reversals of acid flow follow each other in rapid succession,there is no opportunity for coring of the acid, and particles of eachacid ribbon are repeatedly and rapidly brought into direct contact with1 metal cooling surfaces.

The principal function of ribs 30 is to largely 8 I sible, dependingupon the conductivity of the ma.- terial of construction, to space apartthe side walls distances equal to two to twenty times the spacingpermissible in similar but non-ribbed cooler units. The combinedresult-"of the use of the inwardly projecting ribs and the much fartherapart spacing of the side walls is that the total area of the severalchannels 90 as shown onFig. 3 is greatly increased as compared with thetotal area of the passageway between the upper header and the interiorof the cooler in constructions in which the inwardly projecting ribs arenot provided and in which the absence of such ribs requires closespacing of side wall sections such as l2 and 13. On the basis of givenrectangular dimensions (i. e. rectangular dimen sions of the elevationsof Figs. 1 and 2), again depending upon the conductivity of the materialof construction, the invention affords the advantage that capacity of acooler unit may be increased from two-to ten times the capacity of asimilar cooler unit not provided with the inwardly projecting ribs.

The cooling of the acid passing downwardly within the unit may beeffected by a sheet of water or other cooling fiuidfiowing down over theouter surface of the apparatus. The configuration of the corrugationsforming the side walls is such that the cooling liquid flows along thewalls in a. thin, continuously unbroken film. On account of theangularity of the turns and the comparatively short inclined connectingportions constituting theside walls, the liquid adheres to the surfaceof the walls and does not tend to drip off the edges at the convexridges formed by two inclined intersecting surfaces, thus cutting offthe flow of liquid in the concave portions of the wall surface.

Cooling liquid may be supplied in any suitable manner as, for instance,from conduits I I0 arranged alongside the upper acid inlet header.

. Conduits H0 may be supported, e. g. by brackets increase the amount ofmetal heat-conducting surfaces within a minimum space. As will beobserved from Fig. 3,- the inwardly projecting ribs greatly multiply theextent of metal heat-conducting surface in contact with acid as comparedwith constructions. which comprise only side walls such as l2 and I3 anddo not contain the inwardly projecting ribs. In cooler units of thelatter type which do not include inwardly projecting ribs, in order toprovide reasonably satisfactory turbulence, core breaking, and acidmixing as the acid flows down between the outer cooler walls, it isnecessary that the side walls be positioned close together. This limitsthe total area of the acid passageway" between the upper header and theinterior of the cooler unit as defined by the closely spaced side walls,and correspondingly limits the capacity of a unit of given rectangulardimensions. In accordance with this invention, provision of the ribs 30projecting into the body of acid in the cooler unit affords such a greatincrease of metal cooling surface in contact with acid as to make itpos- (not shown) or by any suitable means associated with the coolerunit. The water in the conduits I ll] may be under some pressure andsprayed over the upper outer edge of each side wall through a series ofperforations III in the sides of the conduits immediately adjacentthe'outer surface of the cooler. Such perforations are spaced closely,and act to spray water onto the sides of the cooler in such a mannerthat the cooling liquid forms a substantially even film which flows downover the outer surfaces of the cooler in the form of a thin film.

In the cooler of the modification of Figs. 13-16, i. e. in whichapparatus corresponding ribs on opposed side walls are identicalpatterns, the set of acid channels formed by the inwardly projectingribs onthe front casting of the unit crisscross and are disposed inright angular relationship to the set of acid channels formed by theinwardly projecting ribs on the rear casting of the unit. In use, thecooler of the Figs. 13-16 modification functions generally similarly tothe unit of Figs. 1-4 However, in the embodiment of Figs. 13-16 it willbe understood that, except where inwardly projecting corresponding ribsof the front and rear casting actually abut (in anribs.

mixing caused by the corrugations of the outer walls I2 and I3, theinwardly projecting wavelike ribs on the rear casting, and the inwardlyprojecting but criss-cross related ribs on the front casting, there is aconstant interfiow of acid particles from the acid channels of one setof ribs to the acid channels of the other set of It will be appreciatedthat this crossfiow of acid particles from one set of channels on onehalf of the unit to a cries-cross related set of channels on the otherhalf of the unit provides a still greater degree of turbulence, corebreaking and acid mixing than described above in connection with Figs.1-4.

Figs. 5-8 represent a further modification of my improved cooler. Theoverall structure of this modification is similar to that of thepreferred embodiment shown in Figs. 1-4, except for the arrangement ofthe internal ribs and the passages defined thereby. Included in thismodification are a plurality of equally spaced, parallel, vertical ribsH5 cast integrally at right angles to the inner surface of rear sidewall section III, and a plurality of similar ribs H8 cast on the innersurface of front side wall section I I9. Each of the ribs H5 and H8extends in length from the top header 16 to bottom header II. As seen inFig. 8, in side elevation ribs II5 have the general configuration of therear side wall "1, and ribs II8 bear similar relation to front side wallsection I I9. If desired, ribs H5 and H8 may be cast on the respectivewall sections so that the inner edge of each rib is a straight linewhich lies in a vertical plane passing thru the longitudinal axes ofheaders I6 and I1.

When the front and rear sections [I9 and III of Fig. 8 are boltedtogether to form a unitary structure, corresponding ribs on the opposingside walls are co-extensive, substantially abut each other, and formvertical partitions across the inside of the unit. The space bounded bytwo ad jacent ribs I I5 on one side wall, the two oppositely adjacentribs 8 on the other side wall, and the two side walls form between theside walls a restricted tortuous inner passage which communicates withtop and bottom headers I6 and I1.

Since in the modification shown in Figs. 5 to 8, the ribs are verticalrather than zig-zag as in the embodiment of Figs. 1 to 4, the turbulenceof the acid in the cooler of Figs. 5-8 is brought about by thecorrugations of the side walls. Consequently, in order to prevent thevertical descent .of a quiescent central core of acid without contactinthe side walls H1 and H9, the corrugations should be chosen andconstructed so that the apex (e. g. I) of each inner convex surface ofboth side walls extends at least to and preferably thru a vertical planepassin thru the longitudinal axes of headers I6 and IT. The cooler unitof Figs. 5-8 may be assembled from half-sections cast from identicalmolds.

Although the coolers of the invention have been described as beingconstructed of cast iron, other metals such as stainless steel,aluminum, etc. may be employed.

I claim:

1. Heat exchange apparatus comprising front and rear side plates eachhaving a side wall section, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to form aunitary structure having a, top and a bottom header, said side wallsections being horizontally and relatively parallelly corrugated andbeing spaced apart from each other, the terminal slopes of thecorrugations of each wall section adjacent said headers beingsubstantially parallel, a plurality of inwardly pro- J'ecting ribsattached to the inner face of each wall section, the transverse surfacesof said ribs lying in planes at an angle to' a plane passing through thelongitudinal axes of said headers, said ribs' having a wave-likeprojection on a plane passing through the longitudinal axes of saidheaders, the terminal slopes of each of said inner ribs adjacent saidheaders being substantially parallel, said ribs of both wall sectionsbeing formed so that at least a plurality of portions of the inner edgesof corresponding ribs on opposed sections substantially abut, thereby toprovide between said wall sections a plurality of restricted fluidpassageways connecting said headers.

2. Heat exchange apparatus comprising front and rear side plates eachhaving a side wall section, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to form aunitary structure having a top and a bottom header, said side wallsections being horizontally and relatively parallelly corrugated andbeing spaced apart from each other, the terminal slopes of thecorrugations of each wall section adjacent said headers beingsubstantially parallel, a plurality of inwardly projecting ribs attachedto the inner face of each wall section, the transverse surfaces of saidribs lying in planes at an angle to a plane passing thru thelongitudinal axes of said headers, said ribs having a projection-on aplane passing thru the longitudinal axes of said headers-ofsubstantially the same configuration as a vertical section of a sidewall section, the terminal slopes of each of said inner ribs adjacentsaid headers being substantially parallel, said ribs of both. wallsections being formed so that at least a plurality of portions of theinner edges of corresponding ribs on opposed sections substantiallyabut, thereby to provide between said wall sections a. plurality ofrestricted fluid passageways connecting said headers.-

3. Heat exchange apparatus comprising front and rear side plates eachhaving a side wall section, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to form aunitary structure having a top and a bottom header, said side wallsections being substantially Z-shaped in vertical section and beingspaced apart from each other, the terminal slopes of each wall sectionadjacent said headers being substantially parallel, a plurality ofinwardly projecting ribs attached to the inner face of each wallsection, the transverse surfaces of said ribs lying in planes at anangle to a plane passing through the longitudinaI axes of said headers,said ribs having a substantially Z- shaped projection on a plane passingthrough the longitudinal axes of said headers, the terminal slopes ofeach of said inner ribs adjacent said headers being substantiallyparallel, said ribs of both wall sections being formed so that at leasta plurality of portions of the inner edges of corresponding ribs onopposed sections substantially abut, thereby to provide between saidwall sections a plurality of restricted fluid passageways connectingsaid headers.

4. Heat exchange apparatus comprising front and rear side plates eachhaving a side wall section, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to, form aunitary structure having a top and a bottom header, said side wallsections being substantially Z-shaped in vertical section and beingspaced apart from each other, the terminal slopes of each wall sectionadjacent said headers being substantially parallel, a plurality ofinwardly projecting vertically disposed ribs attached to the inner faceof each wall section, the transverse surfaces of said ribs lying inplanes at a, right angle to a plane passing through the longitudinalaxes of said headers, said ribs having a substantially Z-shapedprojection on a plane passing through the longitudinal axes of saidheaders, the terminal slopes of each or said inner ribs adjacent saidheaders being substantially parallel, said ribs or both wall sectionsbeing formed so that at least a plurality of portions of the inner edgesof corresponding ribs on opposed sections substantially abut, thereby toprovide between said wall sections a plurality of restricted fluidpassageways connecting said headers.

5. Heat exchange apparatus comprising front and rear side plates eachhaving a side wallsection, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to form aunitary structure havin a top and a bottom header, said side wallsections being horizontally and relatively parallelly corrugated andbeing spaced apart from each other, the terminal slopes of thecorrugations of each wall section adjacent said headers beinsubstantially parallel, a plurality of inwardly projecting ribs attachedto the inner face of each wall section, the transverse surfaces of saidribs lying in planes at an angle to a plane passing thru thelongitudinal axes of said headers, said ribs having a projection-0n aplane passing thru the longitudinal axes of said headers-orsubstantially the same-configuration as a vertical section of a sidewall section, the terminal slopes of each of said inner ribs adjacentsaid headers being substantially parallel, said ribs or both wallsections being formed so that at least a plurality of portions of theinner edges of the ribs on one section substantially abut, incriss-cross relation, portions of the inner edges of the ribs of theother section, thereby to provide between said wall sections a pluralityof restricted fluid passageways 12 connecting said headers, said wallsections being of substantially identical construction.

6. Heat exchange apparatus comprising front and rear side plates eachhaving a side wall section, a header portion adjacent the top and thebottom of each wall section, means connecting said plates to form aunitary structure having a top and a bottom header, said sidewallsections 1 being horizontally and relatively parallelly corr'ugatedand being spaced apart from each other, the terminal slopes of thecorrugations of each wall section adjacent said headers beingsubstantially parallel, a plurality of inwardly projecting ribs attachedto the inner face of each wall section, the transverse surfaces of saidribs lyi in planes at an angle to a plane passing thru the longitudinalaxes of said headers, said ribs havins a Projection-on a plane passingthru the longitudinal axes of said headers--of substantially the sameconfiguration as a vertical section of a side wall section, the terminalslopes of each of said inner ribs adjacent said headers beingsubstantially parallel, said ribs of both wall sections being formed sothat the inner edges of corresponding ribs on opposed sectionssubstantially abut throughout their length, thereby to provide betweensaid wall sections a plurality of restricted fluid passagewaysconnecting said headers.

EDWIN B. LOPKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

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